By way of non limitative example, such supports may be fitted between a vehicle chassis and the internal combustion engine of this vehicle for absorbing not only the "hash" oscillations imposed on the chassis through the unevenness and variations of the slope of the ground when the vehicle is travelling over this ground but also the vibrations due to the operation of the engine, particularly when idling, or else at the time of the shocks applied to this engine during starting and stopping respectively by the first and last explosions.
The invention relates more particularly, among the supports of the kind in question, to those which are formed by a sealed case fitted between the two rigid elements, which case has a rigid base able to be fixed to one of the two rigid elements, a rigid annulus which can be fixed to the other rigid element, a resilient annular support wall sealingly connecting the base to the annulus and a flexible membrane connected sealingly to the annulus, the inside of this case being divided, by a sealed dividing wall connected to the annulus between the annular wall and the membrane, into two chambers, namely a work chamber on the annular wall side and a compensation chamber on the membrane side, these two chambers permanently communicating with each other through the above restricted passage, which is advantageously formed by a curved channel situated in the connection zone between the annular wall and the annulus, and a liquid mass filling the two chambers as well as the restricted passage.
The invention relates more particularly still, but not exclusively, to the case where the sealed intermediate dividing wall comprises a deformable or mobile portion forming a floating "valve" and means for limiting the amplitude of the movements of this valve to a low value, preferably less than 0.5 mm.
With such a support, the oscillations or vibrations created between the two rigid elements result in moving these two elements towards or away from each other axially in turn.
Those of these oscillations called "hash" which have a relatively low frequency (less than 20 Hz) and a relatively high amplitude (greater than 0.5 mm) cause the liquid to be driven from one of the two chambers into the other through the restricted passage and conversely and, for a given value of said frequency depending essentially on the dimensions of said passage, high damping of the oscillations considered can be observed because of the resonance effect of the liquid mass flowing through this passage.
In preferred constructions comprising a valve such as defined above, those of the oscillations considered which have a relatively high frequency (greater than 20 Hz) and a relatively low amplitude (less than 0.5 mm) result in corresponding oscillations of the valve without there being a veritable transfer of liquid through the restricted passage, which causes the transmission of the oscillations in question to be filtered from the rigid element where they are generated to the other rigid element.
With known embodiments of supports of the kind in question, the supported weight (engine or similar) is only connected to the carrier structure (vehicle chassis) by the resilient annular wall of the supports.
It may then happen that certain abnormally high forces exerted on the supported mass, such as those due to sudden deceleration or acceleration of the vehicle, result in excessive deformation of these walls which may cause tearing or rupture thereof: the supported mass is then no longer connected to the carrier structure and serious damage may result.
To overcome such a drawback, it has already been proposed to provide the supports considered with:
a rigid ring inside the work chamber and fixed to the rigid annulus,
and a rigid foot axially extending the base inwardly of the work chamber, which foot passes through said ring with a clearance and ends in a projecting sole which cannot pass through this ring.
In such a case, the mutual movements of the base with respect to the annulus in the direction in which these two elements move away from each other, due to the exertion of high forces on the supported mass, are automatically limited by abutment of the sole against the ring.
Such constructions often give satisfaction.
But they have certain drawbacks such as a relatively high overall axial size, a relatively high weight and are difficult to fit.
The object of the invention is especially to overcome these drawbacks.